As methods for producing agrochemical granules, the following methods are known. For example, PTL 1 discloses a production method in which a sustained-release agrochemical composition which contains an agrochemical active component, a hydrophobic substance having a boiling point of 50° C. or higher, a substance capable of absorbing oil, and a hydrophilic substance having a boiling point of 50° C. or higher are melted, and the resultant is granulated by extrusion under a condition of heating performed at a temperature equal to or higher than the melting point. Specifically, PTL 1 discloses a method in which 20 g of acetamiprid as an active substance, 620 g of precipitated calcium carbonate as a carrier, 20 g of polyvinyl alcohol as a release control agent, and 40 g of white carbon capable of absorbing oil are uniformly mixed together, 300 g of molten paraffin wax (melting point of about 70° C.) is added thereto, the mixture is kneaded with a kneader while being kept at a product temperature of 85° C., the kneaded material is granulated by being extruded through a screen, which is heated at 85° C. and has 1 mm openings, then ground with a disintegrator, and then the resultant is sieved and classified into granules of 0.8 mm to 2 mm in size.
PTL 2 discloses a method for producing agrochemical granules composed of an agrochemical active ingredient, a thermoplastic material, and an inorganic diluting carrier, through (i) a mixing step, (ii) a kneading step, and (iii) an extruding step. In this method, extruding granulation is performed at a temperature that is equal to or higher than a freezing point and lower than a melting point of the thermoplastic material. Specifically, PTL 2 discloses a method in which 2% by weight of dinotefuran as an agrochemical active ingredient, 20% by weight of montanoic acid ester wax as a thermoplastic material (melting point of 75° C. to 85° C. and a freezing point of 70° C. to 75° C.), 5% by weight of white carbon as an inorganic diluting carrier, 10% by weight of talc, and 63% by weight of calcium carbonate are loaded in to Henschel mixer and mixed together, the mixture is discharged as a powder at 76° C., the powder is loaded into a screw extrusion granulator (EXR-130) manufactured by Fuji Paudal Co., Ltd. and kneaded at 78° C., the resultant is granulated by being extruded through a die having 0.8 mm openings at 73° C. and then ground by a disintegrator, thereby obtaining granules.
PTL 3 discloses a method for producing an agrochemical composition composed of an agrochemical active ingredient, two or more kinds of hydrophobic substances, a substance capable of absorbing oil, and a carrier, through (i) a mixing step, (ii) a kneading step, and (iii) an extruding step. In this method for producing agrochemical granules, extruding granulation is performed at a temperature that is equal to or higher than a freezing point and lower than a melting point of a hydrophobic substance having a high melting point. Specifically, PTL 3 discloses a method in which 2% by weight of acetamiprid as an agrochemical active ingredient, 15% by weight of carnauba wax (melting point of 83° C. and a freezing point of 73° C. to 74° C.) and 5% by weight of paraffin wax (melting point of 70° C.) as hydrophobic substances, 5% by weight of white carbon as a substance capable of absorbing oil, 2% by weight of polyvinyl alcohol as a water-soluble substance, and 10% by weight of talc and 61% by weight of calcium carbonate as a carrier are loaded into a Henschel mixer and mixed together, the mixture is discharged as a granular material at 80° C., the granular material is loaded into a screw extrusion granulator (EXR-130) manufactured by Fuji Paudal Co., Ltd., kneaded at 80° C., and granulated at the same temperature by being extruded through a die having 0.8 mm openings, and the granules are further ground with a disintegrator, thereby obtaining agrochemical granules.